happstack-server-7.1.7: Web related tools and services.

Safe Haskell | None

Happstack.Server.Error

Description

Some useful functions if you want to wrap the `ServerPartT` monad transformer around the `ErrorT` monad transformer. e.g., ``ServerPartT` (`ErrorT` e m) a`. This allows you to use `throwError` and `catchError` inside your monad.

Synopsis

- spUnwrapErrorT :: Monad m => (e -> ServerPartT m a) -> Request -> UnWebT (ErrorT e m) a -> UnWebT m a
- simpleErrorHandler :: Monad m => String -> ServerPartT m Response
- errorHandlerSP :: (Monad m, Error e) => (Request -> e -> WebT m a) -> ServerPartT (ErrorT e m) a -> ServerPartT m a

# Documentation

spUnwrapErrorT :: Monad m => (e -> ServerPartT m a) -> Request -> UnWebT (ErrorT e m) a -> UnWebT m a

Flatten ``ServerPartT` (`ErrorT` e m) a` into a ``ServerPartT` m a` so that it can be use with `simpleHTTP`. Used with `mapServerPartT'`, e.g.,

     simpleHTTP conf $ mapServerPartT' (spUnWrapErrorT simpleErrorHandler)  $ myPart `catchError` errorPart

Note that in this example, `simpleErrorHandler` will only be run if `errorPart` throws an error. You can replace `simpleErrorHandler` with your own custom error handler.

see also: `simpleErrorHandler`

simpleErrorHandler :: Monad m => String -> ServerPartT m Response

A simple error handler which can be used with `spUnwrapErrorT`.

It returns the error message as a plain text message to the browser. More sophisticated behaviour can be achieved by calling your own custom error handler instead.

see also: `spUnwrapErrorT`

errorHandlerSP :: (Monad m, Error e) => (Request -> e -> WebT m a) -> ServerPartT (ErrorT e m) a -> ServerPartT m a

Deprecated: Use spUnwrapErrorT

This `ServerPart` modifier enables the use of `throwError` and `catchError` inside the `WebT` actions, by adding the `ErrorT` monad transformer to the stack.

You can wrap the complete second argument to `simpleHTTP` in this function.

DEPRECATED: use `spUnwrapErrorT` instead.